Lithiated Stannasilanes – Building Blocks for Monocyclic Si–Sn Rings

Dilithiated di(stannyl)oligosilanes (^tBu₂Sn(Li)– (SiMe₂)_n–Sn(Li)^tBu₂; 4 , n = 2; 5 , n = 3) were synthesized by the reaction of lithium diisopropylamide (LDA) with the α,ω‐hydrido tin substituted oligosilanes (^tBu₂Sn(H)– (SiMe₂)_n–Sn(H)^tBu₂; 1 , n = 2; 2 , n = 3). Surprisingly, the reaction of 1 and 3 (^tBu₂Sn(H)–(SiMe₂)₄–Sn(H)^tBu₂) with LDA resulted not in the formation of the lithiated compound, but what one can find is the formation of the 5,5‐ditert.butyl‐octamethyl‐1,2,3,4‐tetrasila‐5‐stannacyclopentane ( 8 ) (n = 4) in addition to the expected product 4 (n = 4) and the 3,3,6,6‐tetratert.butyl‐octamethyl‐1,2,4,5‐tetrasila‐3,6‐distannacyclohexane ( 7 ) (n = 3). Reactions of 4 and 5 with dimethyl and diphenyldichlorosilanes yielding monocyclic Si–Sn derivatives ( 9 – 11 ) are also discussed. The solid‐state structures of 7 and 11 were determined by X‐ray crystallography.     

Integral enthalpy of mixing of the liquid ternary Au–Cu–Sn system

The integral enthalpy of mixing of the ternary Au–Cu–Sn has been determined with a Calvet type calorimeter at 6 different cross sections at 1273 K. The substitutional solution model of Redlich–Kister–Muggianu was used for a least square fit of the experimental data in order to get an analytical expression for the integral enthalpy of mixing. The ternary extrapolation models of Kohler, Muggianu and Toop were used to calculate the integral enthalpy of mixing and to compare measured and extrapolated values. Additional calculations of the integral enthalpy of mixing using the Chou model have been performed. With the calculated data, the iso-enthalpy lines have been determined using the Redlich–Kister–Muggianu model. A comparison of the data has been made.     

Ortho‐Trialkylstannyl Arylphosphanes by C–P and C–Sn Bond Formation in Arynes

A novel and efficient approach to ortho‐trialkylstannyl arylphosphanes by the reaction of arynes generated in situ with stannylated phosphanes (R₃Sn? PR₂) is described. Concurrent C? P and C? Sn bond formation occurs with high yields, and stannylated products are easily transformed into valuable ortho‐substituted arylphosphanes. The reaction features high efficiency, good regioselectivity, and excellent practicality.     

IR laser‐induced breakdown in tetramethyltin adjacent to Ag or Au: deposition of β‐Sn nanograin‐containing amorphous Au–Sn/C and Ag–Sn/C films

Pulsed IR laser irradiation of metal (Au or Ag) target in gaseous tetramethyltin (TMT) results in metal ablation and adjacent dielectric breakdown (DB) in TMT and allows gas phase deposition of films containing metal (Au or Ag), Sn and C elements. Volatile products of DB of TMT were examined by FT‐IR spectroscopy and revealed as intermediates of gas phase carbonization reactions. The solid films were analyzed by FT‐IR and Raman spectroscopy, X‐ray diffraction and electron microscopy and shown as amorphous nanostructured Au–Sn/C and Ag–Sn/C phases containing β‐Sn nanograins. These Sn nanograins exhibit irreversible amorphization upon heating and melt below the melting point of bulk β‐Sn phase. Copyright © 2012 John Wiley & Sons, Ltd.     

Knudsen effusion mass spectrometric determination of mixing thermodynamic data of liquid Ag–In–Sn alloy

The vaporisation of a liquid Ag–In–Sn system has been investigated at 1273–1473 K by Knudsen effusion mass spectrometry (KEMS) and the data fitted to a Redlich–Kister–Muggianu (RKM) sub-regular solution model. Nineteen different compositions have been examined at six fixed indium mole fractions, X_In = 0.10, 0.117, 0.20, 0.30, 0.40 and 0.50. The ternary L-parameters, the thermodynamic activities and the thermodynamic properties of mixing have been evaluated using standard KEMS procedures and from the measured ion intensity ratios of Ag⁺ to In⁺ and Ag⁺ to Sn⁺, using a mathematical regression technique described by us for the first time. The intermediate data obtained directly from the regression technique are the RKM ternary L-parameters. From the obtained ternary L-parameters the integral molar excess Gibbs free energy, the excess chemical potentials, the activity coefficients and the activities have been evaluated. Using the temperature dependence of the activities, the integral and partial molar excess enthalpies and entropies were determined. In addition, for comparison, for some compositions, also the Knudsen effusion isothermal evaporation method (IEM) and the Gibbs–Duhem ion intensity ratio method (GD-IIR) were used to determine activities and good agreement was obtained with the data obtained from fitting to the RKM model.     

Electron correlation effects at Sn/Si(1 1 1)– and Sn/Ge(1 1 1)– reconstructions

Electron correlation effects for the two-dimensional electron gas associated with the surface bands of the Sn/Si(1 1 1)–3×3, , Sn/Ge(1 1 1)–3×3 and reconstructions are analyzed. Unrestricted local-density-approximation (LDA) calculations enable to define a many-body hamiltonian that includes intra- and inter-site electron interactions. From the analysis of this hamiltonian, it can be concluded that the reconstructions present a Mott transition, while the 3×3 surface remains metallic. How these results can be used to to discriminate between conflicting models explaining the phase transition is described. Inverse photoemission data for the Sn/Si(1 1 1) surface suggests that this phase transition can be explained by means of a dynamical fluctuations model.     

Partial Sn‐atom ordering in Sm3Ga0.80–2.48Sn4.20–2.52

Trisamarium digallide tristannide crystallizes with a partially ordered Pu₃Pd₅‐type structure in space group Cmcm. In a single crystal of Sm₃Ga_1.89(4)Sn_3.11(4), the 8g position is mostly occupied by Sn atoms (93% Sn and 7% Ga), while the 4c and 8f positions are occupied by a Ga/Sn statistical mixture. The evolution of the structure as a function of the Ga content has been studied by X‐ray powder diffraction on ten Sm₃Ga_5−xSn_x samples. It is shown that the 8g position remains occupied essentially exclusively by Sn atoms within the whole homogeneity range, with x ranging from 2.52 to 4.20.     

[Sn9HgSn9]6–: An Intermetalloid Zintl Ion with Two Sn9 Connected by Heteroatom

The title compound [K([2,2,2]crypt)]₁₂[Sn₉]₂[Sn₉HgSn₉] has been obtained by reaction of elemental mercury with the binary phase K₄Sn₉ in ethylenediamine after addition of [2,2,2]crypt and layering with toluene. The X‐ray single crystal analysis shows that the compound consists of two isolated Sn₉ clusters and two Sn₉ clusters connected by a mercury atom.     

Formation of Au/Pd–Sn trimetallic particles onto vitreous carbon

The sequential deposition process of Pd and Sn on Au microcrystals, previously electrodeposited onto vitreous carbon (VC) was investigated in sulphuric acid solution by cyclic voltammetry and Auger electron spectroscopy (AES). Scanning electron microscopy was used to characterize Au deposits. The results reveal that the deposition of Pd and Sn is selective on the Au microcrystals, uniformly distributed on the VC surface, due to the strong interaction energy between the three metals. From the cyclic voltammetric and AES measurements in the VC/Au/Pd/Sn system, the existence of a Sn core–shell structure with Pd can be inferred. Similar voltammetric results were obtained for the VC/Au/Sn/Pd system, where in this case, the Pd adsorbed layer screened the Sn deposits on the VC/Au interface. However, the AES spectrum shows that Sn is still present on the surface, indicating that probably, the Sn deposits have diffused to the surface, or they are not completely covered by Pd. The VC/Au/Pd/Sn modified substrate appears as an interesting electrocatalyst material for the reduction of nitrate ions. Copyright © 2013 John Wiley & Sons, Ltd.     

Cs4Au7Sn2: eine Gold–Zinn-Gerüststruktur mit [Au7]-Clustern und Sn2-Hanteln

Cs₄Au₇Sn₂: a Gold Tin Framework Structure with Au₇ Clusters and Sn₂ Dumb-Bells Silver coloured, brittle single crystals of Cs₄Au₇Sn₂ were synthesized by reaction of caesium azide with gold sponge and tin powder at T = 920 K. The structure of the compound (space group R3m, Z = 3, a = 6.844(1) Å, c = 29.233(5) Å) was determined from X-ray single-crystal diffractometry data. Gold and tin form a framework structure that consists of interconnected [Au₇] clusters and Sn₂ dumb-bells. The caesium atoms accupy channel-like cavities within the gold tin partial structure.     

Ein grünes,paramagnetisches Goldfluorid – Sn1−xAuxF4?

A Green Paramagnetic Gold Fluoride – Sn_1?xAu_xF₄? Green single crystals were obtained by heating (Au-tube, 450° – 500°C) a mixture of SnF₂ and AuF₃ (Sn : Au = 1 : 1) which correspond to the SnF₄-type [2, 3] (two single crystals, A: 762 I_o, R1 = 2.4%; B: 1591 I_o, R1 = 1.2% (SHELXL-93); I4/mmm (No. 139); B: a = 404.8(1) pm, c = 796.4(1) pm, c/a = 1.97, Z_F2 = 0.2354). Due to atom absorption and Mössbauer measurements the crystals contain Au. The compound is paramagnetic and follows the Curie-Weiß law (14.7–251.3 K, θ = ?12 K, μ/μ_B = 1.55). ESR-experiments confirm that Au is surrounded by 6 F^? according to Sn in SnF₄ (2 short (187.5 pm) and 4 longer (202.4 pm) distances). The observed Mössbauer spectra could not be interpreted yet, but they don't correspond to any known.     

Synthesis and Structure of [Sn4Se11]6–, [Sn2Se52–], and [Sn3Se72–] – Model Anions for the Solventothermal Reaction Pathway to Lamellar Selenidostannates(IV)

Reaction of A₂CO₃ (A = K, Rb) with Sn and Se in an H₂O/CH₃OH mixture at 115–130°C affords the isotypic selenidostannates(IV) A₆Sn₄Se₁₁ _. xH₂O (A = K, x = 8) 1 and 2 whose discrete [Sn₄Se₁₁]^6– anions each contain two corner‐bridged ditetrahedral [Sn₂Se₆]^4– species. Similar reaction conditions with A = Cs afford Cs₂Sn₂Se₅ _. H₂O ( 3a ) and Cs₂Sn₂Se₅ ( 3b ) in which such [Sn₂Se₆]^4– building blocks are connected through common Se atoms into infinite [Sn₂Se₅^2–] chains. The [Sn₃Se₇^2–] ribbons of (Et₄N)₂Sn₃Se₇ ( 4 ), formed by treating (Et₄N)I with Sn and Se in methanol at 130°C, can be regarded as resulting from the condensation of [Sn₂Se₅^2–] chains with molecular [SnSe₄]^4– anions. The anions [Sn₄Se₁₁]^6–, [Sn₂Se₅^2–], and [Sn₃Se₇^2–] represent the products of individual reaction steps on the potential condensation pathway of [Sn₂Se₆]^4– to the lamellar selenidostannates(IV) [Sn₄Se₉^2–] or [Sn₃Se₇^2–].     

K6Sn23Bi2 und K6Sn25 – zwei Phasen mit chiraler Clathrat-Struktur und ihr Verhalten gegenüber Ethylendiamin

K₆Sn₂₃Bi₂ and K₆Sn₂₅ – Two Phases with Chiral Clathrate Structure and their Reactivity towards Ethylenediamine K₆Sn₂₃Bi₂ was prepared from the elements in a sealed niobium tube at 620 °C. A single crystal of the composition K₆Sn₂₅ could be isolated from the reaction of a solidified melt of nominal composition ”︁K₄Sn₉”︁”︁ and 18crown6 (1,4,7,10,13,16-hexaoxacyclooctadecane) at 45 °C. K₆Sn₂₃Bi₂ and K₆Sn₂₅ are isotypic and adopt the chiral cubic clathrate structure type cP124. Both crystal structures were determined from single crystal X-ray data: space group P4₃32, a = 16,300(2) and 16,202(2) Å, respectively, Z = 4. The structures contain one kind of a distorted pentagonal dodecahedron of the elements Sn/Bi and Sn, respectively, as the only building block. The pentagonal dodecahedron is centered with potassium and linked by three pentagonal faces and one external bond to four others. Thus leading to a three-dimensional, chiral zeolite-like network. The resulting voids and channels are occupied by potassium. There are 17 four- and 8 three-connected atoms out of every 25 framework atoms. The reactions of the title compounds as well as of solidified melts of the compositions K : Sn = =x : 25 (x = 4; 5; 8; 11 and 22) with ethylenediamine are discussed.     

Ab initio Hartree–Fock–Slater calculations of polysulfanes H2Sn (n = 1–4) and the ions HS and S

An ab initio Hartree–Fock–Slater procedure was applied to the calculation of the electronic structure of polysulfanes, H₂S_n (n = 1–4) and the ions HS and S. Charge densities, overlap populations, and deprotonation energies are calculated; the latter appear well correlated with the first and second acidity constants.     

Über Oxostannate(II). III. K2Sn2O3, Rb2Sn2O3 und Cs2Sn2O3 – ein Vergleich

On Oxostannates(II). III. K₂Sn₂0₃, Rb₂Sn₂0₃, and Cs₂Sn₂O₃ – a Comparison Hitherto unknown Rb₂Sn₂O₃ has been obtained by heating of mixtures of binary oxides [RbO_0.48 + SnO, Rb:Sn = 1.1:1, Al₂O₃?cylinders, Ar] as deep yellow powder or deep yellow single crystals. It is isotypic to K₂Sn₂O₃, R3 m-D with a = 6.086 Å, c = 15.101 Å, Z = 3, d_calc = 4.69, d_obs = 4.64 g X cm^?3. For 260 hkl it is R = 5.2₇% and R_w = 5.0₉% (MoKα, 4-circle diffractometer data). The structure of K₂Sn₂O₃ and Rb₂Sn₂O₃ is compared with that of Cs₂Sn₂O₃. For both types Effektive Coordination Numbers, ECoN, and the Madelung Part of Lattice Energy, MAPLE, have been calculated.     

Electrochemical Reduction of Carbon Dioxide to Methanol on Hierarchical Pd/SnO2 Nanosheets with Abundant Pd–O–Sn Interfaces

Electrochemical conversion of CO₂ into fuels using electricity generated from renewable sources helps to create an artificial carbon cycle. However, the low efficiency and poor stability hinder the practical use of most conventional electrocatalysts. In this work, a 2D hierarchical Pd/SnO₂ structure, ultrathin Pd nanosheets partially capped by SnO₂ nanoparticles, is designed to enable multi‐electron transfer for selective electroreduction of CO₂ into CH₃OH. Such a structure design not only enhances the adsorption of CO₂ on SnO₂, but also weakens the binding strength of CO on Pd due to the as‐built Pd–O–Sn interfaces, which is demonstrated to be critical to improve the electrocatalytic selectivity and stability of Pd catalysts. This work provides a new strategy to improve electrochemical performance of metal‐based catalysts by creating metal oxide interfaces for selective electroreduction of CO₂.     

Sn3N4, ein Zinn(IV)-nitrid – Synthese und erste Strukturbestimmung einer binären Zinn–Stickstoff-Verbindung

Sn₃N₄, a Tin(IV) Nitride – Syntheses and the First Crystal Structure Determination of a Binary Tin-Nitrogen Compound By reaction of SnI₄ with KNH₂ in liquid ammonia at 243 K a white product mixture was obtained. After evaporation of ammonia the solid residue was annealed in vacuum for 2–5 d at 573 K. Subsequently collected x-ray powder diffraction patterns exhibited reflections of KI and a new compound Sn₃N₄. Analogous reactions of SnBr₂ and KNH₂ led to KBr and dark brown microcrystalline Sn₃N₄ but also to metallic tin. The structure of tin(IV)-nitride was determined from X-ray and neutron powder diffraction data: Space group Fd 3 m, Z = 8, a = 9.037(3) Å. Sn₃N₄ crystallizes in a spinel type structure. Both metal atom positions are occupied by tin atoms of oxidation state plus four.